Fuel injector for internal combustion engines



J. G. cADlou 3,249,308

FEL` INJECTOR FOR INTERNAL COMBUSTION ENGINES May 3, 1966 2 Sheets-Sheet l Filed July 51, 1963 ATTORNEYS Jen/v @sarees CAD/ou www May 3, 1966 J, G. cADlou 3,249,308

FUEL INJECTOR FOR INTERNAL COMBUSTION ENGIN Sh s-Sheet 2 Filed July 31, 1965 2 l n 3/ ze L i 5 INVENTOR ATTORNEYS fmass of combustive air;

United .States Patent O 3,249,308 I FUEL INJECTOR FUR INTERNAL COMBUSTION ENGINES Jean Georges Cadiou, Paris, France, assigner to Societe Anonyme Andre Citroen, Paris (Seine), France, a cornpany of France Filed July 31, 1963, Ser. No. 298,995 Claims priority, application France, Aug. 2, 1962, 905,881, Patent 1,344,917 4 Claims. (Cl. 239-453) The present invention relates to fuel injectors for internal combustion engines, and has for an object, improvements therein.

As is known, in order to obtain good combustion in an injection-fed internal combustion engine, it is necessary for the injection system to effect the following operations simultaneously:

s `(a) A fine and uniform atomization of the fuel in th (b) An accurate release of the right quantity of injected for each stroke;

(c) A highly accurate determination of the pressure corresponding to the opening of the valve in4 order to facilitate the adjustment of the injectors and to ensure reliability in operation.

Apart from pneumatic systems in which the fuel is injected by a current of air, and which are little used, there exist mechanical systems in which thefuel is injected without using compressed air, under the action of the pressure of the liquid alone.

Such mechanical injectors are closed under the action of a return spring which returns the valve head onto its seat and whose tension is so adjusted that the needle begins to move only at a predetermined pressure called the calibration pressure.

Some injection devices in which the valve head opens in the direction of ow of the fuel, make use of a phenomenon known as the needle differential effect, which consists of an increase in the surface area over which the pressure is exerted during operation. After the valve has opened, the pressure acts over a section of the needle with a surface area which is effectively greater than that of the valve and thus causes the valve to open rapidly.

Under very light working conditions, such as may arise in car engines which are idling or operating under a very fuel ` low load, there occurs a vibration of the needle (popping action) favorable to good atomization.

The chief disadvantage of such injectors is their high cost of manufacture, chiefly due to the necessity for grinding-in operations and particularly elaborate truing'. It is a question of machining a needle of a more or less comj plex geometrical structure, free to slide in a bore in the body of the injector, while ensuring a perfect hermetic seal when at rest. These two parts are in contact with one another at the level of conica-1 and cylindrical bearing surfaces providing both a seal and an axial guide. It is therefore necessary to produce absolutely coaxial parts.

In one known injector, two cylindrical bearing surfaces on either side of a conical bearing surface simultaneously provide the seal and the guide and also apply the head or moving part of the valve against its seat. The manufacture of this injector is complicated by technological difficulties due to the need to machine 'three absolutely coaxial adjacent bearing surfaces.

Another kno-wn injector, which is more simple to manufacture, has only two distinctly differentiated bearing surfaces. One of these, which is conical, provides the seal, and the other, cylindrical, the axial guide for the needle. But since the needle bears only on one surface, the guiding is not perfect as inthe aforementioned type.

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It is an object of the present invention to provide an accurately operating injector opening in the direction o f flow of the fuel, in which the spindle or needle moves freely along the axis defined by the end bearing surfaces. This is made possible by a simple construction which does not call for perfect alignment of the said bearing surfaces, but avoids the appearance of stress during the movement of the needle.

Accordingly, the inventionconsists in a fuelinjector for an internal combustion engine, having a spindle or needle carrying a valve head or body for application against a seating, wherein the spindle or needlehas three bearing surfaces, of which two are cylindrical and are at the two ends of the spindle or needle, and one is conical and in the neigborhood of the injection valve head, the spindle or needle being guided by said two cylindrical bearing surfaces and the valve seal being provided by the conical bearing surfaces land the cylindrical bearing surface nearer the valve head.

Preferably, the cylindrical portion of the spindle or needle, which is located immediately after the conical valve head, is provided with plane surfaces defining channels opening into an annular discharge orifice. This orifice is limited on the one hand by a bore of larger diameter in the body of the injector and on the other hand by the corresponding cylindrical part of the valve head constituting the bearing surface. The valve head is also provided, at the level of the stage providing both the seal and the guides for the spindle or needle, with chamfers, the number and dimensions of which will be given later on in the description, which ensure the passage of the fuel and also enable the lower end of the spindle or needle to be permanently guided.

Advantageously, the spindle or needle is provided at the end opposite the valve head with a washer ofappropriate shape, through which the tension of the return spring is applied to said valve'head.

The manufacture of such an injector has the advantage that it lies within the scope of present-day precision mechanics. It is trouble-free, since the tolerances required are such that in spite of the small size of the part they may be machined with no particular diiculty.

The present invention also relates,by way of new industrial products, to apparatus in which the present device is used, and to fixed or mobile assemblies, and in particular, motors provided with such apparatus.

In order that the invention shall be more clearly understood, reference will now be made to the accompanying drawings, which show one embodiment thereof purely by way of example, and in which:

FIGURE 1 shows an injector in accordance with the present invention, in the closed position, in diagrammatic axial section;

FIGURE 2 shows a section made along the line A-A through the injector shown in FIGURE l;

FIGURE 3 shows a more detailed view of the needle separated from the injector shown in FIGURE l;

FIGURE 4 is a side View, on a larger scale, of the injection poppet valve in the closed position;

FIGURE 5 is a side View, on a larger scale, of the injection valve in the open position;

FIGURE 6 shows the injection valve in cross-section along the line B-B of FIGURE 3;

FIGURE 7 shows a section of the washer mounted at the upper end of the spindle or needle, and

FIGURE 8 shows the same washer, seen from above.

Referring to the drawings, in an injector according to the invention, a body 1, which has a multi-stage bore axially therein, acts as a feed for fuel under pressure. The said body 1 is housed in an injector-holder 3 and i-s held in position by an end-plug 4 screwed into'a threaded 3 female portion 5 in the said injector-holder 3, the said end-plug 4 carrying a conventional connection 6 for connecting the injector to the injection pump.

The body 1 of the injector has two coaxial cylindrical chambers 7 and 8 which intercommunicate via a narrow co-axial channel 9, and th-rough which the stem of the injector spindle or needle 10 may be passed.

The chamber 7 located at the lower end of the injector comprises a conical seat 11 against which the head lor moving portion 12. of the valve, which is located at the lower end of the injector spindle 10, is applied, and, also a cylindrical bearing surface 13 guiding the piston or slide portion 14 of the valve head, the lower end 15 of this cylindrical bea-ring surface being turned to a slightly larger diameter so as to define, together with the corresponding portion of the spindle, an annular outlet orifice 16.

The chamber 8 provides a seat for a spring 17 bearing on the base thereof and enabling the injector spindle 10 to be guided -by means of a guide sleeve 25 sliding in the upper portion of the said chamber.

With the exception of the valve head, the largest diameter of Vthe stem yof the injection spindle 10 must be less than that of the narrow channel 9, so that it can be inserted into the body of the injector. This spindle is acted on both by the pressure of the liquid to be injected and by the pressure of the return spring 17.

Referring to FIGURES 4 and 5, which show a side view, to a larger scale, of the head of the injector, it will be seen that the valve head 12 has a conical shoulder portion 18 applied again-st the seat 11 and a cylindrical Apiston or slide portion 14 of which the diameter is very slightly less than that of the chamber 7, so as to achieve a satisfactory hermetic seal.

These conical and cylindrical bearing surfaces must be machined with sufiicient accuracy to obtain a satisfactory seal.

The said piston or slide portion 14, which is guided by the bea-ring surface 13, is provided with lateral chamfers such as 19, evenly distributed around its periphery, which define free spaces 20 between the spindle and the body of the injector which enable the fuel to pass through. These chamfers are cut only into the upper portion of the piston or sliding portion (referring to the position shown), so that so long as the injector is closed they cannot open into the discharge orifice 16. 'Iheir number, and thedepth to which they are machined, are determined by the area of the cross-section of the passage it is sought to provide. This area is in the neighborhood of the area of the cross-section of the discharge orifice and depends -both on the minimum volume of liquid to be injected, so as to allow for sufiicient velocity of the jet, and on the maximum volume, so as not to exceed maxi-mum permissible pressure values. Moreover, it has the advantage of remaining constant throughout the entire injection stroke.

The cylindrical piston or sliding portion 14 leads to a throat 21 and then to a divergent conical extension 22 which defiects the jet emerging from the discharge hole and atomizes it. The said conical extension 22 remains permanently outside the body lof the injection 1.

When the needle is closed, the pressure of the fuel is exerted on the circular section of the needle at the level When the force resulting from the pressure exceeds the thrust of the spring, the spindle leaves the seating 11 and the pressure of the liquid is then exerted over the section of the cylindrical piston or sliding portion 14 which has a diameter d2.

As d2 is considerably greater than d1, the force acting on the spindle is increased and the movement of the spindle is considerably accelerated until it reaches the stop position which will be defined hereinafter. At this point `the oW spaces 20 defined by the chamfers 19 and the Vbody of the injector are uncovered and the fuel is forced into the discharge orifice 16, after which it is atomized. 'T he pressure of the ,fluid then decreases until it becomes 'of the output opening of the channel 9 (diameter d1).

equal tothe closure pressure. Injection then ceases. The spring 17 forces the spindle 19 against its seat 11, while the flow spaces 20 are once again blocked. The injector is then ready for a new injection stroke.

The spindle 10 is constituted over the greater part of its length by a 4stem 23, the diameter of which has been reduced in order to reduce its Weight and to allow for the necessary passage of fuel. This stern has an enlarged portion encircled by a bearing surface 24, on which a sleeve is mounted with very slight play. This guide sleeve 25 guides the injection spindle 10 and bears, under the action of the spring, on a washer 26 engaged in a throat 33 on the spindle. The said guide sleeve 25-is provided with a flange 27 which comes into contact at the end of its travel with the upper surface ofthe injector and limits the movement of the valve portion 18, preventing the piston or sliding portion 14 from completely leaving the annular discharge orifice 16l The cylindrical portion 28 which carries the bearing surface l24, slides freely in the bore 29 in the chamber 8, and is provided withchamfers 30 which canbe seen in FlGURE 2 and which enable the fuel to flow directly into the said chamber 8.

In this geometrical arrangement, in which the bearing surfaces are short and localized at the two ends of the spindle 10, it is possible to tolerate a certain eccentricity of the said bearing surfaces, within the limits of play permissible. Thus no supplementary stress is introduced during the movement of the needle, although the conical poppet valve head is` allowed to apply itself firmly against its seating, and although a perfect seal is ensured.

The chamfers 30 communicate at their upper ends with a throat 31 machined in the sleeve under the flange 27, which collects the fuel brought thereto by grooves 38 provided in the upper surface of the body of the injector 1, and allowing for the free passage of the fuel when the flange 27 is applied against the kbody 1.

At its upper end, the spindle is provided under its head 32, with a throat 33 in which the aforementioned washer 26 is engaged, transmitting the thrust of the spring 17 tothe end of the spindle.

A particularly advantageous embodiment of this washer comprises, as can be seen from FIGURES 7 and 8, a metal disk 34 provided with a central bore 35 and a slit 36 running from the said bore to the edge of the disk.

The thickness of the said washer is made such that when the conical poppet valve head bears on its seat and the -guidesleeve 25 rests on the injectorV body via the flange 27, it may just be slipped under the head 32 of the spindle. The depth of the chamfer 37 on the washer corresponds to the path of the spindle when the washer is in position, which yenables this to be accurately defined.

The action of the spring 17 may be modified by the addition of washers placed at the bottom of the base of the chamber 8.

In particular,its compression must be sufficient to hold the valve head against its seat against `the fuel pressure acting at the level of the orifice and tending to force back the spindle so long as the said pressure is less than a predetermined value sufiicient for injection. It is only when the pressure of the fuel reaches and exceeds this value that the spindle is forced back and the injection begins.

What is claimed is:

1. InA a fuel injector of the type comprising a hollow body defining a bore having inlet and outlet ends, a needle longitudinally slidable for a limited distance within said bore, and resilient means biasing said needle in one direction relative to said bore, the improvement which comprises three axially spaced bearing surfaces carried on said needle which engage three mating bearing surfaces on said body, one of the bearing surfaces on said needle being truste-conical and the other two cylindrical, each of the cylindrical bearing surfaces on said body being positioned to be in contact with at least a portion of the mating bearing surface on said needle and thereby guide said needle throughout its longitudinal movement within said bore, the frusto-conical bearing surface on said needle being biased toward its mating surface and positioned between the two cylindrical bearing surfaces on said needle, the diameter of said needle between said bearing surfaces being sufficiently less than that of the encircling portions of said bore to prevent Contact therebetween, said resilient means being positioned between the frusto-concal bearing surface and the cylindrical bearing surface nearest the inlet end of said bore, said cylindrical bearing surfaces forming guides for said needle, and the frusta-conical bearing surface on said needle and the cylindrical bearing surface on said needle nearest the outlet end of said bore forming seals with the mating surfaces on said body when in maximum contact there-with, the cylindrical bearing surface on said needle nearest said outlets end being interrupted by a plurality of inwardly depressed champfers circumferentially spaced about a portion of its len-gth remote from said outlet end and the bore in said body having at its outlet end a short section having a diameter greater than that of said last mentioned cylindrical bearing surface, so that a passage is formed between said needle and bore when, but only when, the bearing surface on said needle nearest the outlet end of the body projects so far beyond the mating bearing surface on said body that only the portion thereof interrupted by said champfers overlaps and is guided by said body bore.

2. A fuel injector as claimed in claim 1, comprising a cylindrical sleeve carried by said needle, the cylindrical bearing surface carried on said needle nearest the inlet 6 end of said bore being formed on the outer surface of said sleeve.

3. A fuel injector as claimed in claim -1 in which said bore denes cylindrical inlet and outlet chambers in which the cylindrical bearing surfaces carried by said body are respectively positioned, and said needle comprises successively a cylindrical portion of larger diameter positioned in said inlet chamber, a neck and a terminal head portion, said injector also comprising a cylindrical sleeve carried by said cylindrical portion of lar-ger diameter, said sleeve being provided with a bearing surface mating with one in said inlet chamber and serving to axially guide said needle, and resilient means positioned between said sleeve and said frusto-conical shoulder and biassing the frusto-conical surface on said needle toward its mating surface.

4. A fuel injector as claimed in claim 3 in 'which said needle is necked near its outlet endl and its terminal portion Iflares conically outward beyond said neck to form an appendage which projects beyond said chamber at all positions of said needle.

References Cited by the Examiner UNITED STATES PATENTS 2,263,197 ll/l941 Tabb et al. 239--453 2,433,985 l/ 1948 Fodor 239-453 2,602,005 7/ 1952 Weldy 239--453 2,921,746 1/1960 Burman 239-453 FOREIGN PATENTS 757,316 7/ 1951 Germany. 530,196 12/ 1940 Great Britain.

EVERETT W. KIRBY, Primary Examiner.

UNITED STATES PATENT OFFICE t CERTIFICATE OF CORRECTION Patent No. 3,249,308 May 3, 1966 Jean Georges Cadiou It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the drawings, Sheets l and Z, in Figs. 4 and 5 the horizontal line tangent to the arcuate line representing the top of the chamfer l9 should be eliminated and replaced by two horizontal lines, one leading from each of the intersections between said arcuate line and a vertical line defining the chamfer to the nearest Vertical line defining the exterior of the piston. In each of Figs 3 4 and 5 the horizontal lines connecting the lower ends of the vertical lines defining the chamfer l9 to the nearest vertical line defining the exterior of the piston should be eliminated.

Signed and sealed this llth day of March 1969.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. IN A FUEL INJECTOR OF THE TYPE COMPRISING A HOLLOW BODY DEFINING A BORE HAVING INLET AND OUTLET ENDS, A NEEDLE LONGITUDINALLY SLIDABLE FOR A LIMITED DISTANCE WITHIN SAID BORE, AND RESILIENT MEANS BIASING SAID NEEDLE IN ONE DIRECTION RELATIVE TO SAID BORE, THE IMPROVEMENT WHICH COMPRISES THREE AXIALLY SPACED BEARING SURFACES CARRIED ON SAID NEEDLE WHICH ENGAGE THREE MATING BEARING SURFACES ON SAID BODY, ONE OF THE BEARING SURFACES ON SAID NEEDLE BEING FRUSTO-CONICAL AND THE OTHER TWO CYLINDRICAL, EACH OF THE CYLINDRICAL BEARING SURFACES ON SAID BODY BEING POSITIONED TO BE IN CONTACT WITH AT LEAST A PORTION OF THE MATING BEARING SURFACE ON SAID NEEDLE AND THEREBY GUIDE SAID NEEDLE THROUGHOUT ITS LONGITUDINAL MOVEMENT WITHIN SAID BORE, THE FRUSTO-CONICAL BEARING SURFACE ON SAID NEEDLE BEING BIASED TOWARD ITS MATING SURFACE AND POSITIONED BETWEEN THE TWO CYLINDRICAL BEARING SURFACES ON SAID NEEDLE, THE DIAMETER OF SAID NEEDLE BETWEEN SAID BEARING SURFACES BEING SUFFICIENTLY LESS THAN THAT OF THE ENCIRCLING PORTIONS OF SAID BORE TO PREVENT CONTACT THEREBETWEEN, SAID RESILIENT MEANS BEING POSITIONED BETWEEN THE FRUCTO-CONICAL BEARING SURFACE AND THE CYLINDRICAL BEARING SURFACE NEAREST THE INLET END OF 